In the industrial field, often, gases are used to cool machines, for example by air or hydrogen. A pressure is exerted on the cooling gas to move the gas through the machine. To prevent leakage of the gas a machine oil can be provided, especially a seal oil. In particular in the field of turbogenerators which generate high power for the public grid an oil seal is provided around the shaft of the turbogenerator to maintain hydrogen pressure inside the turbogenerator. A thin film of seal oil or oil around the shaft prevents hydrogen gas from escaping the turbogenerator. Specific seal oil systems are designed to guarantee the operability of the seal oil in operation. These seal oil systems have to satisfy several functions, as to maintain the oil pressure, slightly higher than the gas pressure of the turbogenerator, to maintain the oil temperature, and to maintain the oil quality. Further functions of the seal oil system comprise adequately segregating the gas side return oil from the air side return oil, removing of oil mists, to prevent mixture of air and gas, to follow the regulations of explosive environments. The process of removing trapped gas or air is called degassing. The operation is performed in two separate tanks to avoid an explosive mixture, air mixed with hydrogen. Further, to prevent oil flow along the shaft inside the turbogenerator. A common seal oil system or oil degassing system for a turbogenerator comprises a degassing tank to receive oil from a drive end of the turbogenerator, another degassing tank to receive oil from a non-drive end, a degassing tank open to the atmosphere, and a vacuum tank to receive oil from the three mentioned tanks. This seal oil system further comprises pumps, coolers or heat exchangers to remove heat from the oil, and strainers or filters. The seal oil system provides the required sealing against the leakage of hydrogen gas from the turbogenerator. Lubricating oil is provided into the shaft of the turbogenerator. The oil pressure is maintained slightly higher than the gas pressure. Typical values of the gas pressure inside the turbogenerator are 5 bars and the oil pressure is 0.3 to 0.5 bars higher. Oil is supplied to both drive end and to the non-drive end of the turbogenerator which is then split into two sides of the seal ring, the air side and the gas side. Return oil from the gas side of both drive end and non-drive end are collected in two separate tanks called degassing tanks. These degassing tanks are designed as pressure tanks to withstand high oil pressures. Return oil from the air side from both the drive end and the non-drive end are manifolded and collected in a further tank. The further tank in this state of the art example is also designed as a pressure vessel and maintained at a negative pressure with the help of suction fans or pumps in order to remove residual air. A further tank is provided which contains a vacuum and maintains a constant vacuum by means of pumps. The oil from the before mentioned three degassing tanks is sucked into the vacuum tank. This seal oil system to degas the oil has a substantial cost of materials related to the number of tanks and especially one tank to provide a vacuum.